A cell maintains a life phenomenon by performing a variety of biological functions, such as gene expression, cell growth, cell cycle, metabolism, signal transduction, and the like, which are mediated by various and complex protein-protein interactions. Accordingly, understanding the nature and function of such intracellular protein-protein interactions has been a major foundation of our understandings of basic cellular processes, and has also played an essential part in our ability to develop new drugs and treat diseases.
A representative method of investigating protein-protein interactions in vitro is an affinity chromatography method.
In the case of protein affinity chromatography, protein has to go through demanding and complex purifying processes. Disadvantageously, since the interactions between proteins are only assessed in vitro, this methodology may result in false-positive results. For example, proteins can be bound by an electrostatic interaction while they pass through a column.
In order to perform a quantitative measurement, a method of investigating the protein-protein interactions according to conventional art technologies analyzes the interactions in the isolation. In other words, the interaction of proteins of interest is assessed in the absence of other intracellular materials by isolating and purifying each of the proteins away from the cellular milieu and analyzing the protein-protein interactions. Disadvantageously, these conventional art technologies limit, or prevent, the ability to analyze the protein-protein interactions at the single molecular level in the context of the normal intracellular environment (e.g., in the presence of other proteins, and the like).
Moreover, methods of investigating protein-protein interactions according to the conventional technologies are also disadvantageous because they do not allow assessment of the degrees of effects that other proteins may have on specific protein-protein interactions in the context of the actual intracellular environment.